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Message-ID: <20201120134746.61626e57@gandalf.local.home>
Date: Fri, 20 Nov 2020 13:47:46 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Philippe Duplessis-Guindon <pduplessis@...icios.com>
Cc: linux-trace-devel@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>,
Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>,
Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: Duplicate fields in event format of `regcache_sync `
On Fri, 20 Nov 2020 12:50:33 -0500
Philippe Duplessis-Guindon <pduplessis@...icios.com> wrote:
> Hi,
>
> I am doing an ftrace plugin for Babeltrace 2 [1], and while I was
> parsing the event fields I had an error saying that `regcache_sync` has
> 2 fields named `type`. The problem seems to come from the
> drivers/base/regmap/trace.h file [2]. This is the patch where this was
> added: [3]. The `int field` type is not assigned, so I was wondering if
> it is normal that the field is there.
>
> This is the format of this event:
>
> $ sudo cat /sys/kernel/debug/tracing/events/regmap/regcache_sync/format
> name: regcache_sync
> ID: 1216
> format:
> field:unsigned short common_type; offset:0; size:2; signed:0;
> field:unsigned char common_flags; offset:2; size:1; signed:0;
> field:unsigned char common_preempt_count; offset:3; size:1;signed:0;
> field:int common_pid; offset:4; size:4; signed:1;
>
> field:__data_loc char[] name; offset:8; size:4; signed:1;
> field:__data_loc char[] status; offset:12; size:4; signed:1;
> field:__data_loc char[] type; offset:16; size:4; signed:1;
> field:int type; offset:20; size:4; signed:1;
>
> print fmt: "%s type=%s status=%s", __get_str(name), __get_str(type),
> __get_str(status)
>
It looks like dumb luck that this ever worked. :-/
The correct fix is to nuke that "int type" field. It's not even assigned.
Thanks for pointing this out.
-- Steve
> Thank you,
>
> Philippe
>
>
> [1] https://babeltrace.org/
>
> [2]
> https://github.com/torvalds/linux/blob/master/drivers/base/regmap/trace.h#L129
>
> [3]
> https://github.com/torvalds/linux/commit/593600890110c02eb471cf844649dee213870416
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